In certain situations, communication between mobile devices and wireless cellular networks may get hindered due to inadequate wireless coverage. This may happen due to natural or man-made obstructions. For example, in-building mobile devices may find it difficult to exchange radio signals with externally located base stations. This can happen due to poor propagation characteristics of radio signals inside concrete buildings.
Direct/Adhoc communication between mobile devices (Device-to-Device (D2D) mode) along with support for wireless Relays is a viable option for data transfer in such scenarios. Devices, which are unable to reach the cellular infrastructure directly, can use D2D mode to exchange data with other devices. Such data can be forwarded further with the help of relay nodes. Unfortunately, most of the currently deployed cellular wireless systems, e.g., GSM, 3G-UMTS or Release 8/9 of 3GPP LTE, support neither the relay functionality nor direct mode communication. Even though the recent standards of LTE technology have incorporated these features, these are yet to be deployed due to their implementation complexity, for example, a Relay node as envisaged in 3GPP LTE standards, is required to support the LTE eNodeB as well as a subset of User Equipment (UE) functionality thereby making it a fairly complex network element. While the LTE D2D solution, in addition to being technically complex, has some limitations such as supporting only single hop relay communication, using a distributed scheme for selection of the relay, and so on, which may not lead to an optimal path for data transfer through the network.
Adhoc/direct mode communication between UEs (User Equipments) can also be achieved by augmenting 3GPP-LTE based UEs with a supplementary Radio communication interface using a suitable wireless technology, such as a Wireless Local Area Network (for example, IEEE 802.11 Wi-Fi), or a Personal Area Network (for example, Bluetooth). Such hybrid networks, using LTE for infrastructure mode communication and a supplementary radio technology for adhoc/direct mode communication between UEs can be used to enhance the coverage of the wireless networks. In such a network, some of the UEs with connectivity to LTE eNodeB and having a supplementary radio interface can act as Relay Nodes between the two networks, i.e., between the LTE network and the adhoc networks. However the solution may not be optimal as the devices communicating in adhoc mode, i.e., without centralized control, may generate substantial interference for each other leading to poor performance of the network overall. This may be an issue in scenarios where multiple groups of users are contending for communication resources simultaneously in a geographical area. Devices in adhoc networks may also face problems related to energy consumption. Due to lack of centralized control, devices with low energy reserve (battery levels) also may participate in receiving/sending data on behalf of others leading to further drainage of battery for such devices. Additionally, direct communication between mobile devices over a supplementary radio link may not be secure, which renders this method almost unusable for use cases such as public safety/mission critical communication, where secure communication between mobile devices may be a critical requirement.